gear pair with negative modified centre distance

例句：

1. 1. The car's engine is running smoothly with the right gear.
   汽车的引擎在正确的档位下运行顺畅。
2. 2. The engineer adjusted the gear to match the speed of the train.
   工程师调整了齿轮，以匹配火车的速度。
3. 3. The old man used to work in a gear shop and was very knowledgeable about them.
   这位老人以前在齿轮店工作，对它们非常了解。